Detection of coherent noise through the output of random quantum circuits

As quantum systems with increasing numbers of qubits emerge, new methods of characterizing and mitigating noise sources are required in the multi-qubit regime. While methods like randomized benchmarking (RB) and its variations are widely used in single and few-qubit systems to characterize coherent and incoherent noise sources, multi-qubit RB quickly becomes prohibitive at current coherence and control limits. In addition, it has been shown in recent experiments with three qubit RB that single and two-qubit RB fail to capture error sources present in larger qubit systems. On the other end of the spectrum, system-level metrics like quantum volume and other methods exist, but lump coherent and incoherent errors together in their output. We present here a method, based on the output of random quantum circuits, capable of quantitatively discriminating coherent noise from incoherent noise in multi-qubit systems.